Many industrial machines (e.g., locomotives, trucks, earth-moving equipment, windmills, and the like) include elements or assemblies (e.g., mechanical drive trains) that operate within difficult environments and/or endure substantial amounts of thermal or torsional stress as well as shock and vibration. It is often desirable to monitor a condition of an element or assembly so that it may be replaced or repaired before severe and permanent damage is sustained by the machine. Often, fluid lubricants are used to provide lubrication and cooling to increase performance of the machine and/or to increase the lifetime operation of the machine. Lubricants reduce the friction between two parts that engage each other and may also dissipate heat that is generated by the friction between the two parts. As one specific example, speed control from a traction motor or other provider of mechanical power may be accomplished with a gear train or drive train. Gear trains typically include at least two gears that engage each other. For instance, teeth of a first gear (e.g., pinion gear) may engage teeth of a larger gear at a gear mesh. It is common for the gears to be lubricated by a lubricant (e.g., oil) to reduce the friction between the gears and to facilitate the dissipation of heat that is generated during operation. For the gears to be suitably lubricated, a designated amount of lubricant is available for use by the gears.
A gear train may include a gear case that surrounds one or more parts of the gear train. The gear case has a reservoir for holding the lubricant. At least one of the gears may move through the reservoir to lubricate the gear and consequently the gear mesh. At least one of the gears may be coupled to a shaft that projects out of the gear case. To prevent leakage from the reservoir or the gear case, the interface between the shaft(s) and the gear case is sealed.
The sealed interfaces, however, are often exposed to harsh conditions. For example, gear trains of locomotives are frequently exposed to large differences in temperature, humid environments, dry environments, abrasive dirt or grime, and/or challenging vibratory states. These conditions may cause a failure in the sealed interface thereby resulting in leakage of the lubricant. When an insufficient supply of lubricant is available for the gears, the machine may be susceptible to gear train or rolling element bearing damage that results in a locked axle condition. In the case of locomotives, locked axles may require the locomotive to be removed from service and sent to a facility for repair. Both the removal and repair of the locomotive may be time-consuming and costly. Furthermore, the lost productivity of the locomotive is also costly.
In addition to having a sufficient amount of lubricant, it is also desirable for the lubricant to have a sufficient quality during operation. For example, lubricants in a reservoir can become contaminated by water, metallic particles, and non-metallic particles. Contaminated fluids may lead to damaged parts or a decreased performance of the machine. In addition, the lubricant may age due to repetitive thermal and viscous cycles resulting in the loss of fluid properties such as viscosity.
Conventional methods of inspecting fluids of a machine include visual inspection of the fluid (e.g., dipsticks) or a sensor that is directly wired to a system. However, these methods may not be practical and/or may have limited capabilities. For example, due to the configuration of some machines, it may be difficult to visually inspect the fluid. Also, hardwired sensors may not be suitable for machines that frequently move and/or are exposed to harsh conditions.
In addition to detecting the quantity and/or the quality of a liquid used by a machine, it may be desirable to obtain other information regarding an operative condition of a machine. For example, when an industrial machine is operating properly, the machine may have known or expected vibratory states. However, when a part of the machine is damaged or otherwise not operating properly, the vibrations of the machine may change. Therefore, it may be desirable to detect the vibrations of certain elements in a machine to monitor a health of the elements, other components of the machine, or the machine overall.